Safety mechanism



Oct. 9, 1962 H. BAYER SAFETY MECHANISM Filed Jan. 25, 1961 Tizi. l.

W15 lm 1b 13 \O/ L9 "La 61/ INVENTOR. HARRY BA YER 32 2| Loli-.a BY

ma@ W @W A noe/vf YS jUnited StatesV Patent O 3,057,084 SAFETY MECHANISM Harry Bayer, Valley Stream, N .Y., assignor to New York Silicate Book Slate Co., Inc., Garden City, N.Y., a corporation of New York Filed Jan. 25, 1961, Ser. No. 84,941 7 Claims. (Cl. 35-67) This invention relates to an automatic safety mechanism suitable for use with a power-driven chalk board in combination with a chalk tray d-isposed adjacent and parallel thereto.

In keeping with present-day conservation of space and function design, chalk boards used for educational and other purposes are constructed to be automatically movable in order to utilize the space for other purposes. Thus, for example, in a school classroom, it is convenient to position a moving picture screen behind a chalk board. In the normal routine of the classroom the chalk board is utilized, thereby hiding t-he moving picture screen from view. However, in case it is desired to show an educational or other moving picture iilm, it is necessary merely to push a button to cause the chalk board to move in a vertical direction and thereby expose the moving picture screen.

In many instances, the chalk board is moved out of the way by causing it to proceed in an upward direction. When the use of the moving picture screen is terminated, it is, of course, necessary to move the chalk boardback to its original position. Again, this is usually accomplished by pushing a button which causes downward movement of the chalk board.

In the usual design, a chalk tray is positioned adjacent to and parallel to the chalk board. As the chalk board is descending into its normal position, there is the danger that either an inanimate object, such as a chalk board eraser, or possibly the lingers or hand of a student will be caught between the chalk tray and the edge of the descending chalk board. If the design of the system is such that the chalk board disappears from view in a downward direction, then the danger of crushing an object is present on the initial downward movement of the chalk board.

It is an object of the present invention to provide an automatic safety mechanism for use in systems embody- 4ing power-driven chalk boards.

It is a further `object of this invention to provide a safety mechanism capable of preventing physical injury which may be caused by crushing a member between a moving chalk board and the stationary chalk tray associated therewith.

Briey stated, the present invention is an automatic stop safety mechanism in a system of a power-driven chalk board reciprocally movable in a vertical direction between two positions displaced one from the other, and a chalk tray comprising a power means connected to said chalk board to move said chalk board from one of said positions to -the other, an electrical circuit comprising in series said power means, an electrical power source, an on-ol switch, two limit switches, the rst of said limit switches positioning said chalk board in the rst of said two positions and the second of said limit switches positioning said chalk board in the second of said positions, said second position being located above said first position, anda safety switch, said chalk tray being spring mounted to permit it to move in a downward direction, said safety switch being opened by the downward movement of said chalk board, whereby the downward movement of said chalk tray de-energizes said power means.

The'invention will be more readily understood when taken in conjunction with the drawings in which:

FIG. 1 is a side elevational view partly in section of Patented Oct. 9, 1962 a power driven chalk board in combination with a chalk tray embodying the present invention;

FIG. 2 depicts the structure of FIG. l and shows how a finger may be caught between the chalk tray and `the descending chalk board, and

FIG. 3 is a schematic diagram of one embodiment of an electrical circuit employed in conjunction with the present invention.

With respect now to the drawings and more particularly to FIG. l, there is depicted a side elevational View partly in section of a chalk tray 10 and chalk board 11. The chalk tray 10 is of the conventional type having depressed areas 12 for the storage of chalk.

Chalk board 11 is shown in part only, the depicted portion including face 13, backing 14 and frame 15.

The section of the chalk tray 10 which is related to the present invention is indicated broadly by reference numeral 10 in FIG. l. As shown, this structure involves movable bracket 17 and compression springs 18. Movable bracket 17 is provided with pins 19 which move through slots provided in protruding lip 20 of chalk tray 10.

Also shown in FIG. l is safety switch 21, composed of two contacts 22 and 23. Contact 22 is immovably connected to chalk tray 10 whereas contact 23 is immovably connected to pin Z4. Pin 24 is immovably connected to movable bracket 17. Thus, downward movement of bracket 17 causes contacts 22 and 23 to separate thereby opening switch 21. Electrical connection to contacts 22 and 23 is made through leads 25 and 26, respectively.

FIG. 2 depicts the manner in which an object, such as a finger 16, may be caught between descending chalk board 1,1 and part 17 of chalk tray 10. The presence of an object such as a finger 16 in the path of downwardly moving chalk board 11 causes movable bracket 17 to move downward against the bias of compression springs 18. A very slight downward movement is suincient yto open switch 21 by separating contacts 22 and 23. As shown in FIG. 2, switch 2i1 is open. As discussed in conjunction with FIG. 3, the opening of switch 21 prevents further downward movement of chalk board 11 thereby averting possibly injury to linger 16.

FIG. 3 depicts one embodiment of an electrical circuit suitable for use in conjunction with the present invention. Two separate electrical circuits are depicted in FIG. 3, one of which' comprises an electrical motor 27 which is serially connected with manually operated on-off switch 2S and limit switch 29. This circuit is employed to produce upward movement of chalk board 11.

The other circuit in FIG. 3 depicts electrical motor 30 which is serially connected with manually operated onotf switch 31, limit switch 32 and safety switch 21. This circuit is employed to produce a downward movement of chalk board 11.

With respect now to a detailed discussion of the operation of the present invention, it is assumed that chalk board 11 is in its normal position as shown in FIG. 1 of the drawing. In this position, limit switch 32 is engaged by protrusion 33 attached to frame 15. This engagement maintains switch 32 in the open condition thereby preventing any further downward movement of chalk board 11.

To move chalk board 11 in an upward direction, on-oif switch 28 is closed. Since the chalk board is not in contact with the upper limit switch 29, this switch is closed. Accordingly, closing switch 28 energizes motor 27 (not shown in FIGS. l and 2) and chalk board 11 thereby moves in an upward direction. When upper limit switch 29 is engaged, it is opened thereby deenergizing motor 27 and preventing any further upward movement.

When it is desired to return chalk board 11 to its noramamos-i mal position, switch 31 is closed. Since chalk board 11 is at the top position, limit switch 32 is also closed. Thus, assuming that safety switch 21 is closed, as shown in FIG. 1, electrical motor 30 is energized and chalk board 11 is caused to move in a downward direction.

FIG. 2 depicts how the safety mechanism of the present invention precludes physical injury to an object such as finger 16 which is in the path of downwardly moving chalk board 11. The pressure of frame of chalk board 11 against finger 16 is transmited to movable bracket 17. Movable bracket 17 moves in a downward direction by compressing springs 18. This downward movement opens contacts 22 and 23 of safety switch 21, therby de-energizing motor 30. Accordingly, the further movement of chalk board 11 is prevented.

The electrical circuits of FIG. 3 are intended to be merely one embodiment suitable for use with the present invention. It is, of course, obvious to one skilled in the art that a single electric motor may be employed to prevent upward and downward movement by using suitable reversing circuits. Furthermore, any type of power means may be used, provided the downward movement of chalk tray 10 may be used to de-energize the power means within a very short time interval.

It is to be appreciated that compression springs 18 are chosen so that a minimum of pressure is necessary to produce downward movement of bracket 17.

FIGS. l and 2 depict the dangers involved in the return movement of chalk board 11 from an upper position to a lower position. It is to be appreciated that the same type of hazard exists in the movement of chalk board 1v1 from its normal position to a lower position.

The embodiments described above are intended as illustrative of the present invention and variations may be made therein by one skilled in the art without departing from the spirit and scope of this invention.

I claim:

l. The combination of a vertically movable chalk board wherein the vertical movement is provided by power means connected to said chalk board, a chalk tray rigidly positioned immediately adjacent and parallel to said chalk board, said chalk tray comprising a bracket which is spring mounted to permit movement in a downward direction, and a switch means connected to said power means and responsive to the downward movement of said bracket, the actuation of said switch means by said downward movement of said chalk tray de-energizing said power means whereby the further movement of said chalk board is prevented.

2. An automatic vstop safety mechanism in a system of a power-driven chalk board reciprocally movable in a vertical direction and a chalk tray rigidly disposed immediately adjacent and parallel to said chalk board comprising electrically operated power means producing upward and downward movement of said chalk board, an electrical circuit for supplying current to said power means, said circuit comrpising in series said power means, an electrical power source, an On-off switch, and a safety switch, said chalk tray comprising a bracket which is spring mounted to permit movement in a downward direction, said safety switch being opened by the downward movement of said bracket, whereby the downward movement of said bracket de-energizes said power means.

3. An automatic stop safety mechanism in a system of a power-driven chalk board reciprocally movable in a vertical direction between two positions displaced one from the other, and a -chalk tray comprising a power means connected to said chalk board to move said chalk board from one of said positions to the other, an electrical circuit comprising in series said power means, an electrical power source, an on-off switch, two limit switches, the first of said limit `switches positioning said chalk board in the first of said two positions and the second of said limit switches positioning said chalk board in the second of said positions, said second position being located above said rst position, and a safety switch, said chalk tray comprising a bracket which is spring mounted to permit movement in a downward direction, said safety switch being opened by the downward movement of said bracket, whereby the downward movement of said bracket de-energizes said power means.

4. In a combination of a chalk board reciprocally movable in a vertical direction between a rst position and a second position in response to a power means, said second position being located below said first position, and a chalk tray rigidly disposed parallel to said chalk board immediately adjacent the lower edge of said chalk board when said chalk board is in said second position, said chalk tray comprising a bracket longitudinally coextensive therewith, an automatic safety mechanism comprising a spring mounting for said bracket permitting said bracket to move in a downward direction, a safety switch responsive to the downward movement of said bracket, said safety switch being connected to said power means and adapted to de-energize said power means, whereby the downward movement of said bracket de-energizes said power means thereby preventing further movement of said chalk board. v

5. The automatic safety mechanism of claim 4 in which said power means is electrically energized, in which said safety switch is connected in the electrical circuit of said power means, and in which the downward movement of said bracket opens said safety switch.

6. In a combination of a chalk board reciprocally movable in a vertical direction between a first position and a second position in response to an electrically operated power means, said second position being located below said rst position, and a chalk tray rigidly disposed parallel to said chalk board and immediately adjacent the lower edge of said chalk board when said chalk board is in said second position, said chalk tray comprising a bracket longitudinally coextensive therewith, an automatic safety mechanism comprising a spring mounting for said bracket permitting said bracket to move in a downward direction, an electrical circuit for energizing said power means cornprising a safety switch serially connected between said p'ower means and an electrical energy source, said safety switch being opened in response to the downward movement of said bracket from said first position to said second position, whereby the downward movement of said bracket opens said safety switch thereby de-energizing said power means and preventing further movement of said chalk board.

7. An automatic stop safety mechanism in a system of a power-driven chalk board reciprocally movable in a vertical direction between an upper and a lower position and a chalk tray rigidly disposed immediately adjacent and parallel to said chalk board comprising a first and a second power means connected to said chalk board, the rst power means adapted to move the said board in an upward direction and the second power means adapted to move the board in a downward direction, the first power means connected in a first electrical circuit comprising switch means to energize said power means, the second power means connected in a second electrical circuit comprising switch means to energize said second power means and a safety switch serially connected therewith, said chalk tray comprising a bracket longitudinally coeXtensive therewith, said bracket being spring mounted to permit movement in a downward direction, and said safety switch being opened by the downward movement of said bracket, whereby the downward movement of said bracket opens said second electrical circuit.

References Cited in the file of this patent UNITED STATES PATENTS 

